I dont know but make sure your palkia is at least level 80.
At level 80 it learn Aqua Tail and at level 90 Aura Sphere.
You are not able to get Aura Sphere as a TM unless you hack. If you can't/do not want to hack then you will be still be able to get it the harder way. You can get any legendary (discluding Arceus) and level it up to level 100. When it gets to level 100 it will learn Aura Sphere. Lucario learns it at Level 34. Palkia, Dialga, and Giratina learn aura sphere at level 90.
Do you mean Aura SPHERE? The following Pokemon learn Aura Sphere in HGSS: Mewtwo, Mew, Lucario, Togekiss, Dialga, Palkia, and Giratina.
Mewtwo learns Aura Sphere at level 93.
Lucario learns Aura Sphere at level 51.
yes. If your riolu evolves after level 37 it will not learn aura sphere. lucario learns aura sphere at lv 37
27 my lucario learnt aura sphere lv37
spacial rend,aura sphere,earth power,slash.
Lucario learns Aura Sphere at level 37.
I believe at level 70.
lv70 spacial rend lv80 aqua tail lv90 aura sphere. i am shire